Looks like I actually have to do this now, eh? Well, at least it's linear. I can do linear. In fact, there might not really be much "game" to this, but in the end, I guess my goal is always to give the sense of having visited a space. But I do know that actually moving around a space requires me to create a lot of assets. So I may have to get creative on that front.
My initial thought is to use the structure (just the structure) of a traditional JRPG: The "level" is a straight line from beginning to end. There are two mini-bosses and a final boss between you and the end. And perhaps there are little inconsequential enemies dotted along the line as well.
The "level" is the tower (power plant). The goal is to get to the top. Or maybe the center.
The bosses will be the three guardians of the plant. Defeat the three guardians to win the game. Now, you aren't the one who will be fighting the battles. Your partner, in his tiny offensive apartment, will do all of the fighting for you. In fact, you may be entirely in the role of moral support (healing). You can't see well enough to fight effectively anyway. You certainly won't be fighting the trash mobs, but perhaps you will have some input on the bosses.